An operating brake valve of the above type is known from DE-05 3841749. Here, the position sensor is housed in the body of the double valve for the combined inlet/exhaust valve and hence in the exhaust duct leading to the atmosphere. The operating brake valve is employed in the scheme of a braking system with more than one circuit in which the brakes are actuated using means of compression and in which the braking circuit assigned to the front axle of the motor vehicle is controlled via the pneumatic section of the operating brake valve. An electrical signal is obtained from the position sensor, which reproduces the path of the thrust piece in the operating brake valve housing, and fed to an electronic control unit. From here, a second braking circuit, assigned to the rear axle of the motor vehicle, branches off as an automated sequence control. This second braking circuit is operated electrically, in fact depending on the first circuit which can be actuated pneumatically. The control unit enables other parameters to also be brought in to modulate and influence the braking pressure in the second circuit.
An operating brake valve is known from EP-0 267 881 B1 in which a linear potentiometer is assigned to the thrust piece to act as a position sensor for retarded control. An operating brake valve is known from DE-PS 26 19 775 in which the electrical control of a retarder is carried out via a multiple contact switch which is wired in the path of the thrust piece.
A multicircuit braking system for heavy road vehicles is known from DE-OS 33 44 252 in which an operating brake valve is used which is designed to be partly pneumatic and partly electric. A pneumatic control of the brake cylinder for the front axle is carried out via the pneumatic part. A sensor is housed in the electric part and this sends a current signal to an electronic control unit which, in the first place, electrically controls the braking circuit assigned to the rear axle. However, the electronic control unit also controls solenoid valves which are assigned to the front axle braking circuit. The respectively higher supply pressure is sent to the brake cylinder as braking pressure via 2-way valves.